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problems with afocal photography

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#1 shan1987

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Posted 21 June 2013 - 09:10 PM

so I've just started my very first endeavor in astrophotography. All i have is a point and shoot digital camera, my 130mm f6.9 reflector and a universal orion camera mount. The camera mount works great for lining up the shot and the camera takes good photos for not being a slr type but not matter how hard i try i always get a giant black blip in the middle of the photo where the secondary mirror is. It never shows up through the eyepiece when i look in, but the camera picks it up every time... I have an old refractor too that i took this picture with(my first astrophoto every!!)so i dont think its a camera issue but its a 70/700 f 10 with a horrible mount(toys-r-u special) . Any suggestions to make the secondary mirror in the reflector to not show up?

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#2 Jeff2011

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Posted 22 June 2013 - 12:01 AM

I would first suggest you collimate your reflector. What is the type and brand of your telescope?

#3 shan1987

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Posted 22 June 2013 - 12:13 AM

its a skywatch(made by orion) i have yet to collimate it since ive owned it but i dont have a laser so....i guess there is no time like the present to learn

#4 Wouter D'hoye

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Posted 22 June 2013 - 09:07 AM

Hi,

This issue has very little to do with collimation. it's not unusual to see the central obstruction. When i took flatswith my VC200L i'd see the spider vanes and the central obsruction in the flats. if the flats pick it up it will also be in the images. Your only option would be to take flts and apply these to your images to get rid of it.

Kind regards,

Wouter.

#5 fishonkevin

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Posted 22 June 2013 - 12:54 PM

I would say that your P&S camera is focusing on the secondary mirror. Does your camera do autofocus?

#6 NeilMac

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Posted 22 June 2013 - 06:28 PM

make sure you do not have macro focus engaged.

#7 Ekyprotic

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Posted 24 June 2013 - 12:35 AM

I have had good results getting rid of my secondary obstruction (granted this is with a SCT), by using a higher powered EP (and no reducer) and also focusing the camera at infinity.

#8 Driven1

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Posted 24 June 2013 - 07:10 PM

I've encountered the same issue using a webcam afocally. What I've found, especially with lower power EP's, that it's an alignment issue. If I get the camera positioned just right, I can get rid of the spot. This is on a very well collimated scope too.

#9 jhayes_tucson

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Posted 24 June 2013 - 07:44 PM

I agree with many of the comments here. If you are doing afocal photography, the camera needs to be focused at infinity. Lock the camera focus and and focus the telescope at infinity as best you can by looking through it. Then position the camera lens about where you had your eye behind the eyepiece. If you set it up correctly, you will not see the secondary shadow.

John






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